Browsers

My recommendations:

macOS/iOS: Safari
other: Chrome

Versions of all "major" browsers:

browser β developer nightly platforms
Safari* Technology Preview Webkit macOS/iOS (T.P. & Webkit on macOS only)
Chrome* β Dev Canary macOS/iOS*, Windows, Linux/Android
Opera* β Developer macOS/iOS*, Windows, Linux/Android
Firefox β Developer/Aurora Minefield macOS/iOS*, Windows, Linux/Android
Edge‡ β Windows 10
 
* originally developed the HTML renderer Webkit (based on KHTML) for Safari as open source.
  Chrome uses Blink (Chromium), based by Google on Webkit.
  Opera also uses Blink. So does Samsung Internet.
  The proxy browser UC Browser uses U3, based on Webkit.
  iOS browsers are restricted by  to use Webkit.
‡ Replaced Internet Explorer:
Windows XPVista7,810
runs IE 8911Edge

Mailers

My recommendations:

macOS/iOS: Mail
browser elsewhere: iCloud
browser w/o iCloud account: Gmail

(Don't even think about using one named after a tree.)